1. Field of the Invention
The present invention relates to a passive cooling system of a nuclear power plant, and more particularly to a passive cooling system in which a method for removing the heat from a secondary coolant system required to cool a nuclear core is implemented, in an event of an accident of a nuclear power plant using a natural circulation method.
2. Description of the Related Art
An auxiliary feedwater system is provided in a nuclear power plant to ensure safety in operating a nuclear reactor.
The auxiliary feedwater system is used to maintain a steam generator level when a primary feedwater system is not operable such that a nuclear reactor cooling system is shifted from a hot standby state into a cold shutdown state.
When an accident occurs in the nuclear power plant, a decay heat (or residual heat) can be removed through a steam generator of a secondary coolant system (or an auxiliary system) in order to cool nuclear fuels loaded on a nuclear core.
In a prior art, a condensing storage tank and an auxiliary feedwater pump are used to perform a heat removal operation through the steam generator. A feedwater system using a pump requires a power and, when the power is not available, the feedwater system is not operable.
Such conventional cooling system of the nuclear power plant is disclosed in Korea Patent Publication No. 2002-0037105, which is published May, 18, 2002.
In the conventional cooling system, when a feedwater is supplied to the steam generator for a cooling operation, the core decay heat (or residual heat) conveyed from a primary coolant system can be removed in the steam generator.
However, such conventional cooling system is of an active type, which can be operated only by an electricity supply. Thus, the conventional cooling system has a problem such that it cannot be operated when an accident occurs in which the electricity supply is interrupted.